1. Field of the Invention
The present invention relates to a method and apparatus for rolling mill control ideally suited to continuous rolling mills arranged in tandem, and more particularly relates to a method and apparatus for obtaining a desired strip crown and strip flatness.
2. Description of the Related Art An example of the prior art is a control system aimed at achieving a target strip crown and target strip shape described under the title "High precision rolling in hot strip mills" (authors: Yasuyuki Nishiyama, Nobuji Shibao, Satoshi Shimazu et al) on pages 79-90 of the Iron & Steel Institute of Japan Rolling Theory Section's 100th Symposium "Rolling Technology. and Theory: Development and Future Trends" (June 1994). As initial set-up functions, this control system has functions for determining the initial set values of work roll pair-cross angle and work roll bending force in each stand for achieving a target strip crown and target strip shape.
The aforementioned system uses the strip crown ratio heredity coefficient and shape coefficient for improving the precision of strip thickness in the transverse direction, but the actual determination of these coefficients has been beset by difficulty.
Moreover, the account of the aforementioned system makes no mention of utilizing the results from rolling of the previous strip, i.e. strip rolled earlier in time sequence when successive stock material is rolled with the rolling mill, for rolling the next strip, i.e. strip rolled later in time sequence; and makes no mention of the case where the rolling conditions are different for the previous strip and next strip.